This study investigates the effect of accelerated aging and type of adhesive on the interlaminar fracture toughness of an Al alloy/CFRP bonded joint in a saltwater immersion test. CFRP (PAN-based carbon fiber) and A7075P-T6 were used as test materials, and Araldite Standard and Loctite EA 9396 AERO were used as adhesives. The DCB test was used to evaluate the mode I interlaminar fracture toughness (GIC). Saltwater immersion tests were conducted with 5 mass% NaCl in the immersion solution for 24 hours and 48 hours. The GIC decreased with increasing immersion time. The results showed that the GIC decreased with the increase in the immersion time. It was found that the GIC of the Loctite adhesive specimen under the 48 h immersion condition was significantly reduced compared to the Araldite adhesive specimen. Besides surface observations were conducted on the crack propagation surface of the specimens after the tests. As a result, the corrosion rate of Loctite bonded specimens was faster than that of Araldite bonded specimens. This suggests that the difference in adhesives may have a significant effect on corrosion.

Semi-solidification forging aims to achieve a near-net shape by forging a slurry in a semi-solidification state using a die. Compared to casting and cold forging, it has the advantages of better dimensional accuracy and smaller forming load. Furthermore, semi-solidified materials can be expected to have improved mechanical properties compared to ordinary materials. In this research, we increased the amount of aluminum added to magnesium alloy, which is considered to be lightweight among practical metals and has excellent mechanical properties such as high specific strength and electromagnetic shielding properties, compared to conventional materials for the purpose of increasing strength.AZX1712 and AZX2112 were selected as materials. We actually carried out semi-solid forging using a servo press and verified the feasibility of molding. As a result, it was possible to produce test pieces for both materials. Moreover, when AZX1712 was used, it was possible to manufacture a test piece having no defect in appearance.

To investigate metal flow of workpiece and flow of lubricant at the die–workpiece interface during cold forging with lubricant, the interface between glass die and commercially pure aluminum workpiece with colored lubricant was in-situ observed during cold forward extrusion type forging by a microscope with a high-speed camera. The lubrication state was evaluated by the pixel value of the recorded image of the interface during forging. The pixel value increased with thinning trapped lubricant at the interface.

Burr changer was proposed to change vertical burr to horizontal burr. The burr changer was attached to inside of a side dam plate. Lower edge position of the burr changer was the most important factor to change the vertical burr to the horizontal burr. A383 aluminum alloy was cast at roll speeds of 30 and 60 m/min. There was not difference between the strip and horizontal burr after cold rolling and annealing.

A twin wheel caster equipped with rotating side dam plate was proposed to cast wire with rectangular cross section. Poring method suitable for this wheel caster was investigated. The wire which width was 5 mm and area of the cross section was ranging from 11 mm2 to 18 mm2 was cast at speed 4 m/min or 5 m/min.

We report on twin roll casting using a commercial-scale device of aluminum alloy Al-3mass % Mg. Twin roll casting is able to produce a strip directly from the molten metal. Thus this process can reduce total cost of strip manufacturing. Many papers on strip casting have been reported, but there are few reports of research using commercial-scale equipment. In this study, we conducted a study of vertical twin roll casting of aluminum alloy Al-3mass % Mg using a commercial-scale device for the purpose of practical application of strip casting. In this study, we investigated the effect of roll speed on strip. The roll diameter is 1000 mm and the width is 240 mm. The roll material is SKD61. The fixing conditions for the strip are a pouring temperature of 660 °C, an initial roll gap of 1.5 mm, and a solidification distance of 100 mm. Strips were created at the roll speeds of 5 m/min, 8 m/min, and 10 m/min. At 5 m/min, the strip was the thickest and had few cracks. At roll speed 10 m/min, the strip thickness was the thinnest and there were many cracks. Metallic luster was observed at all roll speeds.

Strip casting of aluminum strip for casting was tried using a vertical type high speed twin roll caster and unequal diameter twin roll caster. Used alloys were AC4C，AC4CH，AC3A，AC8A，ADC12, AC7A and 2%Si added AC7A. Ductility of aluminum alloys for casting were improved by the rapid solidification using the twin roll caster. For example, the AC3A contains 11%Si, however, cup test could be conducted and limiting drawing ratio was 2.0. Eutectic Si became fine grain, and this made ductility excellent.

SiC/SiC composites are expected to be used as materials for the next generation aircraft engines. The purpose of this study is to improve the thermal performance of SiC/SiC composites by MI method. In the conventional MI method, Si is infiltrated into the composites, however, Si remains in the matrix. In this study, the Si-Ni-Ti alloy was infiltrated into the SiC/SiC composites. In this study, we infiltrated a Hi-Nicalon type S unidirectional fiber preform with Si-Ni-Ti ternary alloy made by arc-melting at 1600℃ and observed the mechanical properties and microstructure of the fabricated composites. The microstructure of the SiC/SiC composites showed that a dense matrix was formed and there were various phases in the matrix. Elemental analysis results showed that the matrix contained not only Si but also Ni and Ti. The pushout test results indicated that the SiC/SiC composites based on the Si-Ni-Ti alloy had a strong interfacial bonding. According to these results, fiber coating and optimization of the fabrication process will be required in the future.

All-oxide composites were fabricated by vacuum impregnation and pressure-less sintering. The mechanical properties of the all-oxide composites with the matrix densified by fine alumina particles and high yield of alumina precursors were investigated. Dense matrix was formed with uniform Vickers hardness independent of the location in the composite. The tensile test results showed low strength due to the strong fiber/matrix interface. This result suggested that introduction of fiber coating that suppresses interfacial bonding is required in addition to the densification of matrix for improving strength. Then, the fiber-matrix interface was produced via dip-coating fiber using Layer by Layer (LbL) assembly mechanism.

Biaxial bending test of alumina ceramics was conducted. Crack initiation behavior was characterized by acoustic emission (AE) technique. Using elliptical specimens, unbalanced biaxial stress state was obtained. The strain measurement during tests demonstrated that the stress ratios were controlled to designated value. The rapid increasing point of cumulative AE energy was recognized during tests. Source location was conducted by the arrival time difference between the signals of the four AE sensors and wave velocity. Since fracture origin observed on the fractured specimen showed good agreement with AE source location, the stress at the rapid increase points in cumulative AE energy was defined as the critical crack formation critical stress. It was confirmed that the final fracture took place after stable crack propagation followed by unstable crack propagation. The average strength of the elliptical specimens was corrected considering the size effect of strength. It was confirmed that the maximum principal stress criterion was appropriate as fracture criterion of the crack initiation. Consequently, fundamental insights for improving reliability of ceramics structures was obtained.

TiO₂ photocatalysts are novel materials that exhibit excellent decomposing organic pollutants under UV/visible light irradiation. Researchers are focusing applications to purify air, wastewater, antivirus, deodorization and so on. In this paper, the processing and performance enhancing of TiO₂ photocatalyst balls by Mechanical Coating Technique and oxidation or acid bath treatment are reported. The cells and units with TiO₂ photocatalyst balls for purification of wastewater are designed and produced.

CuO nanowires have attracted much attention due to their excellent electrochemical properties and are being investigated for various applications such as electricity storage devices and sensors. However, a problem is that the Cu substrate and the oxide film tend to exfoliate at the interface. In this study, the effect of the surface roughness of the Cu substrate on delamination suppression was experimentally determined. The results showed that the apparent exfoliation strength increased as the surface roughness of the Cu substrate was increased. Field emission scanning electron microscopy (FE-SEM) observations showed that the length and density of CuO nanowires were independent of the surface roughness of the Cu substrate. Transmission electron microscopy (TEM) observations confirmed that the CuO nanowires with a rough surface of the Cu substrate had the same twin crystals as the CuO nanowires with a flat surface of the Cu substrate.

A novel method of tape casting followed by spark plasma sintering (SPS) was applied to prepare CuAlO₂ compacts. During the tape casting process, plate-like Al₂O₃ particles distributed along the flow direction of slurry under the action of the shear-thinning effect. It greatly elevated the orientation degree of the CuAlO₂ compacts formed during the following SPS. Meanwhile, to dope Mg to CuAlO₂, MgO powder was added to the received material powders. The results show that sample TC-1273-CuAlO₂-Mg(1%+5%) exhibited the highest thermoelectric performance with a ZT value of 0.0902 at 973 K. Effect of orientation degree, Mg adding and reaction compounds on thermoelectric properties were discussed.

Epoxy adhesives to bond carbon fiber reinforced plastics (CFRPs) have attracted engineers to realize the lightweight joint due to the excellence in the mechanical properties and environmental resistance. However, the rare phenomenon of mal adhesion “weak bond” is needed to investigate the factors for applications of high reliabilities. In previous studies^1-3), the authors showed that saltwater mist contamination consumes epoxy rings to form weak bonds. Based on the results, we report in this work the results of visualization of epoxy equivalents using a scanning electrochemical microscope (SECM). Saltwater contaminated surface of epoxy adhesive shifts the pH to alkaline by the consumption of H⁺ ions and remaining OH^- ions. Variations of contamination level appeared in the visualization plot for the samples of Loctite EA9396 AERO epoxy paste adhesive (Henkel) showing the potentials for the diagnosis and the factor-search of weak bonds.

Tilted Fiber Bragg Grating (TFBG) sensors is an optical fiber sensor with a diffraction grating tilted small angle. TFBG sensors has Bragg resonance, the ghost mode resonance and the cladding mode resonance. It is known that strain and refractive index (RI) can be measured individually analyzing appropriately these resonances. The RI corresponds to degree of cure of epoxy resin, hence TFBG sensors is expected to apply to cure process monitoring of carbon/epoxy laminates and epoxy film adhesive. However, simultaneous measurement of strain and RI has not been established, and a TFBG sensor has not been applied to cure process monitoring of carbon/epoxy laminates. This study demonstrated the applicability of the TFBG sensor for cure process monitoring of carbon/epoxy laminates. Firstly, a simultaneous measurement method of strain and RI was developed by using the TFBG sensor. by using a simultaneous measurement method, RI and strain in curing process monitoring of carbon/epoxy laminates were measured. As a result, the RI due to curing of carbon/epoxy laminates were successfully measured by using the cladding mode. The strain due to thermal expansion and shrinkage could be measured by using the Bragg resonance. Thus, the TFBG sensor is useful to measure RI and strain in cure process monitoring of carbon/epoxy laminates.

A technique for the measurement of in-plane coefficient of thermal expansion (CTE) of ceramic coatings was developed. The surface of a self-standing mullite coating as an environmental barrier coatings (EBCs) for ceramic matrix composites (CMCs) applied to hot sections of jet engines was observed by a blue-laser scanning microscope with a pin hole during the cooling from 1400 °C to room temperature. Thermal expansion was measured from a series of obtained images at various temperature by digital image correlation (DIC), and the CTE of the coating in the in-plane direction was determined. Accuracy and reliability of the measurement were evaluated using a c-plane sapphire plate of which CTE was well established. Surfaces of the coatings adhered on the substrate with various thickness were also observed and the surface thermal expansion were measured. The effects of constraint by the substrate and bending of the coating/substrate system due to the thermal expansion mismatch were discussed.

The characterization of the processing-induced defects is a significant step for developing defect-free processing, which is important to the assurance of the mechanical reliability of brittle ceramics. Recent advances in multiscale X-ray computed tomography which consists of micro-CT and nano-CT enables us to observe the three-dimensional (3D) internal structure non-destructively. Micro-CT reveals the distribution of defects in the entire body of a sample, while nano-CT reveals the shape of the identified defect. This powerful imaging tool was used to reveal the complicated 3D morphology of defects evolved during sintering of alumina. The hierarchical packing structure of granules was the origin of several types of strength-limiting defects, which could not be eliminated due to the differential sintering of heterogeneous microstructures. This imaging technique of internal defects provides a link between the processing and the fracture strength for the development of structural materials.

In order to ensure the safety and reliability in research and development of high temperature structural materials, it is important to develop an experimental technique to visualize the deformation distribution at elevated temperature for understanding deformation and fracture mechanisms quantitatively. In the present study, the principle of stereo observation is combined with the DIC method to develop a device for measuring three dimensional deformation using a high temperature observation system. Experimental results showed that proposed experimental facility was possible to measure surface deformation in three dimensions up to 800℃. Furthermore, air knife is effective in removing thermal haze and is very important for the accuracy of high temperature measurements. It was shown that the newly developed device is capable of measuring deformation in three dimensions in the temperature range up to 800℃ and that the measurement accuracy at each temperature is within a certain margin of error.